Sampling time for Method TO-9a

Ask the Expert Question:

We have procured several PUF sample trains from TestAmerica to test for dioxins and furans using EPA Method TO-9a. The method specifies a usual sampling time of 24 hours to obtain a sample air volume of between 325 to 400 m^3. We will probably run our sampler no longer than 60 minutes with a total sample volume collected of about 20 m^3. The 60 minute sample time bounds the time frame of the emissions we are trying to measure. Any additional time could introduce the potential for confounding sources to be captured in the sampler. Is this a concern of running the sampler less than the "usual" 24 hours from a MDC perspective or is the 24 hours just a convention specified in the method?

                 

Experts Response:

The time recommendations cited in the Method are for relative reference purposes only, and are called out to show the volumes collected over that period of time as examples. There should be no deleterious effects to smaller sample volumes aside from higher reporting limits. If reporting limits are an important issue to your project, and they cannot be obtained by your 60 minute duty cycle, then you should consider more sampling during operational times when correct conditions are regained. That’s how incinerators are tested after a malfunction. Nothing should logically prevent multiple-sampling cycles of your test conditions when they occur. Your custom sampling implementation could take into consideration startup and shutdown, as needed.

Please also note that we often prepare a different apparatus of sampling media for much smaller air volumes than collected on a standard Hi-Volume sampler. The ORBO (click here to see attached picture) is prepared for battery operated pumps, and could be put much closer to your sources. They are very easy to handle.

View Dr. William Anderson's Experts profile

What is the difference between total metals vs. dissolved metals analysis and what form the metal is being analyzed

Ask the Expert Question: 

Can you explain the difference between total metals versus dissolved metals analysis and what form of the metal is being analyzed?

Expert Repsonse: 

Total metals analysis for water samples include the metals content both dissolved in the water and present in the particulates in the water. Typically a dissolved metals analysis of a water sample is performed by removing the particulates with a filter, then analyzing the filtered water for metals. The most common filters used for this purpose have a 0.45 um pore size.

Total metals analysis results should always be greater than or equal to dissolved metals analysis results, because dissolved metals is a subset of total metals. Dissolved metals are generally considered more mobile and biologically available. Thus, the dissolved metals results are useful for risk assessment and fate & transport studies.

The specific metal species (or form) present in the dissolved fraction is highly dependent on the metal of interest. Most of the dissolved species are solvated metal cations such as Na(I) or Cr(VI). Some metals species are present as oxy anions such as arsenite.  

Water solubility of the elemental metals (i.e. neutral valence state) is generally quite low. For example this website states elemental mercury [Hg(0)] has a water solubility limit of 56 ug/L at 25C (http://www.inchem.org/documents/cicads/cicads/cicad50.htm#2.1).

Most regulations use total metals results because it is often considered more conservative and protective, however, depending on the purpose of the regulation it might be based on dissolved or total metal concentrations.

View Dr. Mark Bruce's Experts profile.

What are the differances and applications of HRGC/HRMS and GC-MS/MS instruments

Ask the Expert Question:

What is the difference between the HRGC/HRMS and GC-MS/MS instruments?
What are its major applications?

Experts Response:

By definition HRGC/HRMS stands for “High Resolution Gas Chromatography/High Resolution Mass Spectrometry” and GC-MS/MS stands for “Gas Chromatography/Tandem Mass Spectrometry”.

Starting with the GC-MS/MS, this equipment is fitted with what can be described as a dual mass spectrometry and are generally triple quads (or 3 quadrupoles).  Using a triple quad versus a standard GCMS give greater sensitivity (i.e. allows for lower detection limits from sub part per billion to sub part per trillion) and give greater resolution than a standard GCMS.  For example a standard GCMS can resolve masses 1 atomic mass unit apart.  A triple quad can resolve masses ~1000 atomic mass units apart.  Using GC-MS/MS resolution increase allows for much greater selectivity than standard GCMS.  Another feature of the GC-MS/MS is the dynamic range is much greater than a normal GCMS. 

HRGC/HRMS is a completely different type of instrument for very specific applications.  This instrument is fitted with a huge magnet and has electric sectors, lens and a 6 to 8 foot flight tube.  Using this type of configuration jumps the resolution to 10,000 atomic mass resolutions.  You can separate molecules that may have the same retention time but different masses 0.0001 amu apart.  Also the HRGM/HRMS allows for sensitivity to sub parts per quadrillion level and below and you can easily see 0.5fg on column of 2,3,7,8-TCDD (which is difficult to impossible for a standard GCMS or GC-MS/MS to see).  The dynamic range for the HRGC/HRMS is greater than 2000 times the low point so there is a lot of room to see the low end and the high end without saturating the detector.

There are many methods written for both types of instruments and you can use them for specific needs.  If you are looking for gross contamination then a GCMS is the way to go for general screening and for analytes with little public health risk.  GC-MS/MS is perfect for confirmation of low level GCMS results.  If you are looking to confirm low level results of analytes with high public heath risk then the HRGC/HRMS may be a better option.

EPA Issues National Guidance to Address Proper Maintenance, Removal, and Disposal of PCB-Containing Fluorescent Lights

Release date: 12/29/2010

Contact Information: Tisha Petteway, petteway.latisha@epa.gov, 202-564-3191, 202-564-4355 Dale Kemery, kemery.dale@epa.gov, 202-564-7839, 202-564-4355

WASHINGTON – The U.S. Environmental Protection Agency (EPA) today released guidance recommending that schools take steps to reduce potential exposures to PCBs from older fluorescent lighting fixtures. The guidance, part of EPA’s ongoing efforts to address potential PCB exposures in schools, is based on evidence that the older ballasts contain PCBs that can leak when the ballasts fail, leading to elevated levels of PCBs in the air of schools that should not represent an immediate threat but could pose health concerns if they persist over time.

The guidance document is available online at http://www.epa.gov/pcb.

Polychlorinated biphenyls, or PCBs, are man-made chemicals that persist in the environment and were widely used in construction materials and electrical products prior to 1978. PCBs can affect the immune system, reproductive system, nervous system and endocrine system and are potentially cancer causing if they build up in the body over long periods of time.

“As we continue to learn more about the potential risks of PCBs in older buildings, EPA will work closely with schools and local officials to ensure the safety of students and teachers,” said EPA Assistant Administrator for Chemical Safety and Pollution Prevention Steve Owens. “This guidance on safely addressing the risks from PCB-containing light fixtures is part of EPA’s ongoing efforts to protect the health of our children and provide them with safe, healthy learning environments.”

Until the late 1970s, PCBs were commonly used as insulators in electrical equipment because they have a high tolerance for heat, do not easily burn, and are non-explosive. EPA banned the processing and distribution in commerce of PCBs in 1979 pursuant to the Toxic Substances Control Act due to their toxic effects. However, uses of older PCB-containing ballasts were allowed to continue, provided that the ballasts had not failed and the PCBs were not leaking.

EPA believes many schools built in the U.S. before 1979 have light ballasts containing PCBs. A recent pilot study of three schools in New York City found that many light ballasts in the schools contained PCBs and had also failed, causing the PCBs to leak and contributing to increased levels in the air that school children breathe. EPA regional offices have also worked with school officials to address leaking PCBs in light ballasts in schools in Oregon, North Dakota, and Massachusetts.

Given their widespread use before they were banned, if a school was built before 1979 or has not had a complete lighting retrofit since 1979, the fluorescent light ballasts probably contain PCBs. Although intact, functioning ballasts do not pose a health threat, these lighting ballasts will all fail in time. For that reason, EPA recommends older PCB-containing lighting ballasts should be removed, whether as part of a previously scheduled lighting retrofit program or a stand-alone project.

Schools that have older ballasts should examine them to see if they have failed or if PCB leaks are present. If a light ballast is leaking PCBs, federal law requires the immediate removal and disposal of the PCB-containing ballasts and disposal of any PCB-contaminated materials at an EPA approved facility.

To prevent exposure if leaking ballasts are discovered, school personnel should wear protective clothing, including chemically resistant gloves, boots, and disposable overalls while surveying the ballasts. Replacement of leaking ballasts should be performed in a well-ventilated area, or supplemental ventilation or respiratory protection should be provided to reduce the potential for breathing in fumes.

While replacing lighting ballasts requires an upfront investment, there are state, federal and private funding programs available to potentially provide funding. In addition, replacing older ballasts with newer lighting fixtures will result in energy savings that will increase energy efficiency in schools and likely pay for itself in less than seven years, depending upon hours of operation and local energy costs.

EPA has also developed information on how to properly handle and dispose of PCB-containing fluorescent light ballasts and properly retrofit lighting fixtures to remove potential PCB hazards.

In September 2009, EPA issued guidance to communities about potential PCB contamination in the caulk of pre-1978 buildings. EPA also announced additional research into the potential for PCBs in caulk to get into the air. Research on that and other issues related to PCB exposures is ongoing.

School districts, building owners and others desiring technical guidance should contact EPA at 1-888-835-5372.
Parents who are concerned their children may be attending a school with PCB-containing ballasts should ask their schools whether they have a plan to address PCBs in their schools.

More information on PCBs: http://www.epa.gov/pcb

Information on handling and disposing of PCB-containing light ballasts: http://www.epa.gov/epawaste/hazard/tsd/pcbs/pubs/waste.htm

PCBs hotline: 1-888-835-5372

Source: U.s. Environmental Protection Agency (2010, December). EPA Issues National Guidance to Address Proper Maintenance, Removal, and Disposal of PCB-Containing Fluorescent Lights. Retrieved January 3, 2011 from http://yosemite.epa.gov/opa/admpress.nsf/0/6C03FDEC1E63274C8525780800693D7D